Photodynamic therapy (PDT) in early central lung cancer: a treatment option for patients ineligible for surgical resection

Aptamer-based tumor-targeted drug delivery for photodynamic therapy

A specialized G-rich DNA structure, G-quadruplex, has been studied for its special physical characteristics and biological effects. Herein we report a novel strategy of using G-quadruplex as a drug carrier to target cancer cells for photodynamic therapy (PDT). A G-quadruplex forming AS1411 aptamer could be physically conjugated with six molecules of porphyrin derivative, 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP4), to fabricate the apt-TMP complex. The TMPyP4 molecules in the complex were identified to bind tightly to the aptamer by intercalation and outside binding. Because the G-quadruplex structure is known to target the overexpressed nucleolin in cancer cells, in this study, the effect of the G-quadruplex structure as a carrier for the delivery of TMPyP4 into cancer cells by nucleolin-mediated internalization was investigated. The results showed that the apt-TMP complex exhibited a higher TMPyP4 accumulation in MCF7 breast cancer cells than in M10 normal epithelium cells. After treated with light for 180 s, the photodamage in MCF7 cells was larger than in M10 cells. These results indicated that the TMPyP4 delivery and uptake were mediated by the specific interaction of the apt-TMP complex with nucleolin on the cellular surface and that the use of the AS1411 aptamer as a drug carrier may be a potential tactic in cancer therapy.

Outcome of photodynamic therapy using NPe6 for bronchogenic carcinomas in central airways >1.0 cm in diameter

PURPOSE

Most centrally located early lung cancers (CLELC) <1.0 cm in diameter do not invade beyond the bronchial cartilage, and photodynamic therapy (PDT) with Photofrin is currently recommended as a treatment option for such lesions. NPe6 is a second-generation photosensitizer, and because it has a longer absorption band (664 nm) than Photofrin (630 nm), we hypothesized that NPe6-PDT would exert a strong antitumor effect against cancer lesions >1.0 cm in diameter, which are assumed to involve extracartilaginous invasion and to be unsuitable for treatment with Photofrin-PDT.

EXPERIMENTAL DESIGN

Between June 2004 and December 2008, 75 patients (91 lesions) with CLELC underwent NPe6-PDT after the extent of their tumors had been assessed by fluorescence bronchoscopy for photodynamic diagnosis and tumor depth had been assessed by optical coherence tomography.

RESULTS

Seventy cancer lesions < or =1.0 cm in diameter and 21 lesions >1.0 cm in diameter were identified, and the complete response rate was 94.0% (66 of 70) and 90.4% (19 of 21), respectively. After the mass of large tumors and deeply invasive tumors had been reduced by electrocautery, NPe6-PDT was capable of destroying the residual cancer lesions.

CONCLUSION

NPe6-PDT has a strong antitumor effect against CLELCs >1.0 cm in diameter that have invaded beyond the bronchial cartilage, thereby enabling the destruction of residual cancer lesions after mass reduction of large nodular- or polypoid-type lung cancers by electrocautery. The PDT guidelines for lung cancers should therefore be revised because use of NPe6-PDT will enable expansion of the clinical indications for PDT.

The effect of photodynamic therapy on tumor angiogenesis

Photodynamic therapy (PDT), the activation of a photosensitive drug in tumor tissue with light of specific wavelength, has been used effectively to treat certain solid tumors. Though therapeutic responses are encouraging, PDT-mediated oxidative stress can act as an angiogenic switch that ultimately leads to neovascularization and tumor recurrence. This article explores the effect of PDT on angiogenesis in different tumor models. Overexpression of proangiogenic vascular endothelial growth factor, cyclooxygenase-2 and matrix metalloproteases has often been reported post-illumination. Recent clinical studies have demonstrated that inhibiting angiogenesis after chemotherapy and radiotherapy is an attractive and valuable approach to cancer treatment. In this review, we report the effective therapeutic strategy of combining angiogenesis inhibitors with PDT to control and treat tumors.

Emergent management of malignancy-related acute airway obstruction

Acute obstruction of the airway in the emergent situation results from a wide variety of malignant and benign disease processes. Acute management involves establishing a secure and patent route for adequate gas exchange. This requires rapid determination of the location of the obstruction and nature of the obstruction followed by a thoughtful management approach based on findings. Difficult anatomy, hemorrhage, dense secretions, inflammation, and bulky tumor mass can significantly complicate the task of clearing the airway. Obstruction of the central airways by malignant tumor is associated with poor prognosis, but quality of life is considerably improved by restoration of adequate central airways. For both the patient and the clinician, the presentation can be frightening, and advanced interventional pulmonary/endobronchial techniques are required to achieve prompt relief of symptoms. The alleviation of central airway obstruction by tumor is most often palliative, with improvement of quality of life the primary goal rather than cure. This review will cover covers an approach to the patient with airway obstruction that results from malignancy involving the trachea or proximal bronchial tree and affecting gas exchange.

Results of long-term follow-up of photodynamic therapy for roentgenographically occult bronchogenic squamous cell carcinoma

BACKGROUND

Photodynamic therapy (PDT) is considered a useful and minimally invasive modality for treating centrally located early lung cancer. To date, there has been limited information on the long-term outcome of patients treated with PDT, especially those who are medically operable.

METHODS

Beginning in 1994, patients with roentgenographically occult bronchogenic squamous cell carcinoma (ROSCC) who met our criteria underwent PDT at Tohoku University Hospital and were followed up through 2006. Our criteria were as follows: (1) ROSCC without distant metastasis; (2) medically operable by means of lobectomy or further resection; (3) longitudinal tumor length of <or= 10 mm; and (4) superficial bronchoscopic tumor findings.

RESULTS

A total of 48 patients with ROSCC underwent PDT. The complete response (CR) rate was 94% (45 of 48 of patients). Nine patients (20%) had local recurrence after CR. A total of 11 deaths was observed, with 6 resulting from multiple primary lung cancer and only 1 from the original ROSCC. The 5-year and 10-year overall survival rates for all 48 patients were 81% and 71%, respectively. The Cox proportional hazard model showed that only metachronous multiple primary lung cancer was an independent poor prognostic factor.

CONCLUSIONS

PDT is thought to be a first-line modality for patients who have ROSCC with a tumor length of <or= 10 mm, even if the tumor is medically operable. Most local recurrence can be cured by active therapy such as surgery, radiotherapy, or PDT. Multiple primary lung cancer subsequent to PDT is an important issue from the viewpoint of survival.

Phototoxic aptamers selectively enter and kill epithelial cancer cells

The majority of cancers arise from malignant epithelial cells. We report the design of synthetic oligonucleotides (aptamers) that are only internalized by epithelial cancer cells and can be precisely activated by light to kill such cells. Specifically, phototoxic DNA aptamers were selected to bind to unique short O-glycan-peptide signatures on the surface of breast, colon, lung, ovarian and pancreatic cancer cells. These surface antigens are not present on normal epithelial cells but are internalized and routed through endosomal and Golgi compartments by cancer cells, thus providing a focused mechanism for their intracellular delivery. When modified at their 5′ end with the photodynamic therapy agent chlorin e₆ and delivered to epithelial cancer cells, these aptamers exhibited a remarkable enhancement (>500-fold increase) in toxicity upon light activation, compared to the drug alone and were not cytotoxic towards cell types lacking such O-glycan-peptide markers. Our findings suggest that these synthetic oligonucleotide aptamers can serve as delivery vehicles in precisely routing cytotoxic cargoes to and into epithelial cancer cells.

How to establish a solitary and localized VX2 lung cancer rabbit model? A simple and effective intrapulmonary tumor implantation technique

BACKGROUND

The purpose of this study is to establish a simple and effective technique for the generation of an intrapulmonary tumor model that yields solitary, localized intrapulmonary tumor, and to analyze the highlights of the technique.

METHODS

After being anesthetized by slow intravenous injection of pentobarbital without oral endotracheal intubation, a right intercostal incision was made between the fifth and sixth ribs or at the next intercostal space; the inferior lobe of the right lung was exposed. A 16-gauge needle contained a strip of tumor tissue in the distal portion which connected to a 1.0-mL syringe that contained 0.1 mL air inside, was inserted into the parenchyma at an estimated depth of 1.0 cm, and the air was injected quickly to eject the tumor tissue into the pulmonary parenchyma. The air was drawn from the chest cavity by a race track, and the chest was closed. Thirty animals (Group A) received intrapulmonary tumor implantation (IPTI) as described above, and 16 animals (Group B) received IPTI using a suspension of small tumor fragment. Eight animals in each group were monitored by computed tomography (CT) scanning (Group CTA and CTB) and were used to determine survival time. Twenty-two animals in Group A and 8 animals in Group B were sacrificed and dissected at 21 d post-IPTI, followed by histological examination.

RESULTS

Tumor take rate (tumor developed anywhere in the chest) was 80% in Group A (24/30) and 75% in Group B (12/16); there was no significant difference (P = 0.987). The rate of total chest seeding was significantly higher in Group B (66.7%, 8/12) than in Group A (12.5%, 3/24; P = 0.002). At 3 wk post-IPTI, solitary, localized tumor foci developed at the implantation site in 70% of Group A (21/30); this rate was significantly higher than the 18.8% rate of tumor foci development in Group B animals (3/16; P = 0.001). Twelve of the 16 animals monitored by CT scanning developed tumors. Among them, 7 animals that developed localized intrapulmonary tumors at early time post-IPTI survived significantly longer than the remaining 5 animals that developed extrapulmonary chest seeding tumors (P = 0.001). Intrapulmonary nodules after IPTI may develop granulomas, which were identified by histological examination. Unidentified nodules were detected in CT images, which gradually decreased in size and eventually disappeared.

CONCLUSION

We establish a simple and effective method for the generation of an intrapulmonary tumor model that yields solitary, localized intrapulmonary tumor. The highlights of this technique are tumor quality control and tumor dissemination control. Extrapulmonary chest seeding at early time post-IPTI contributes to short survival. It is necessary to characterize the intrapulmonary nodules using histological methods prior to the evaluation of therapy; this approach may lead to a more accurate determination of therapeutic outcomes.

PDT in early central lung cancer

Resources are needed to use the full potential of photodynamic therapy